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Area Forecast Discussion

774
FXUS62 KCHS 311554
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1054 AM EST SAT JAN 31 2015

.SYNOPSIS...
HIGH PRESSURE WILL PUSH SOUTH INTO THE AREA TODAY. THE HIGH WILL
SHIFT INTO THE ATLANTIC SUNDAY...WHILE A WEAK COASTAL TROUGH
DEVELOPS AND LIFTS NORTH AHEAD OF A COLD FRONT PASSING OVER THE
AREA MONDAY. HIGH PRESSURE WILL THEN RETURN TO THE REGION BY
TUESDAY...BEFORE SHIFTING OFFSHORE AHEAD OF ANOTHER STORM SYSTEM
APPROACHING FROM THE GULF OF MEXICO BY LATE IN THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
LOW-LEVEL HIGH PRESSURE WILL REMAIN OVER THE AREA WHILE HIGH
PRESSURE BUILDS ALOFT AS WELL. THIS WILL MEAN DRY CONDITIONS
PERSISTING AND COOLER THAN NORMAL TEMPS. SKIES WILL BE GENERALLY
SUNNY WITH SOME HIGH CLOUDS STREAMING IN FROM THE NORTHWEST. HIGHS
WILL AVERAGE OUT IN THE MID 50S...COOLEST NORTH OF CHARLESTON AND
WARMEST NEAR THE ALTAMAHA RIVER IN SOUTHEAST GEORGIA. IMMEDIATE COASTAL
LOCATIONS WILL REMAIN CLOSER TO 50 DEGREES AS WINDS BECOME ONSHORE.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
TONIGHT...DEEP LAYERED RIDGING WILL REMAIN FIRMLY ENTRENCHED
ACROSS THE SOUTHEAST U.S. TONIGHT WITH THE CENTER OF THE SURFACE
HIGH FORECAST TO SHIFT SLOWLY OFF THE SOUTH CAROLINA COAST. THICK
CIRRUS ASSOCIATED WITH A SHORTWAVE ROUNDING THE WESTERN FLANKS OF
THE MEAN RIDGE AXIS WILL SPREAD QUITE A BIT OF HIGH CLOUDINESS
ACROSS THE REGION AFTER MIDNIGHT. 31/00Z NSSL-WRF/GEM SIMULATED
CLOUD PRODUCTS SUGGEST SKIES WILL GENERALLY REMAIN PARTLY TO
MOSTLY CLOUDY. THE INCREASED CLOUD COVER COUPLED WITH WEAK
925-850 HPA WARM AIR ADVECTION WILL YIELD A WARMER NIGHT THAN THIS
MORNING WITH LOWS RANGING FROM THE LOWER 30S INTERIOR SOUTHEAST
SOUTH CAROLINA TO THE MID-UPPER 30S ELSEWHERE...EXCEPT THE LOWER
40S ALONG THE BEACHES AND BARRIER ISLANDS.


SUNDAY...SURFACE HIGH PRESSURE WILL BE STEADILY SLIPPING FARTHER
INTO THE ATLANTIC DURING THE MORNING HOURS...JUST DOWNSTREAM OF A
DEEPENING LOW PRESSURE SYSTEM MOVING INTO THE TENNESSEE VALLEY BY
MIDDAY. A WEAK COASTAL TROUGH WILL DEVELOP ALONG THE PERIPHERY OF
THE RETREATING HIGH PRESSURE EARLY...SHIFTING TOWARD THE COAST AND
LIFTING NORTH AS A WARM FRONTAL FEATURE LATE IN THE DAY. THE
FORECAST AREA WILL LIKELY REMAIN BETWEEN MARINE SHOWERS TO THE
EAST/NORTHEAST AND CONVECTION TO THE WEST ASSOCIATED WITH THE
APPROACHING COLD FRONT. HAVE THUS WAITED UNTIL LATE AFTERNOON TO
INDICATE ISOLATED TO SCATTERED SHOWERS SPREADING INTO THE FORECAST
AREA. DESPITE THICKENING CLOUD COVER...TEMPERATURES WILL BECOME
QUITE WARM FOR EARLY FEBRUARY WITHIN SOLID SOUTHERLY FLOW. EXPECT
TEMPERATURES TO PEAK IN THE MID TO UPPER 60S AWAY FROM THE LOCALLY
COOLER COAST.

SUNDAY NIGHT AND MONDAY...A ROBUST UPPER TROUGH WILL SWEEP TOWARD
THE EAST COAST AND ASSIST IN THE PROGRESSION OF THE COLD FRONT
THROUGH THE FORECAST AREA DURING THE MORNING HOURS MONDAY. LOW
TEMPERATURES SUNDAY NIGHT WILL BE QUITE MILD IN THE 50S DUE TO THE
COMBINED EFFECTS OF INSULATING CLOUD COVER AND A WELL MIXED
ATMOSPHERE WITHIN SOLID SOUTHWEST FLOW. THE HIGHEST RAIN COVERAGE IS
EXPECTED FROM SUNSET SUNDAY THROUGH EARLY MONDAY MORNING...WHEN BEST
FORCING FOR CONVERGENCE ALONG THE FRONTAL ZONE AND THE NOSE OF A 130
KT UPPER JET MOVES INTO THE AREA. DUE TO SOME SLIGHT TIMING
DIFFERENCES IN THE MODELS...WILL KEEP RAIN CHANCES JUST BELOW 80
PERCENT...WHICH IS STILL A FAIRLY HIGH CONFIDENCE FORECAST. THE
FRONT WILL LIKELY BE OFFSHORE BY MONDAY AFTERNOON...WITH DRIER AIR
BEGINNING TO FILTER INTO THE REGION AHEAD OF BUILDING HIGH PRESSURE.
RAIN CHANCES WILL THUS END FROM WEST TO EAST AS THE DAY PROGRESSES.
HIGH TEMPERATURES MONDAY AFTERNOON WILL BE WITHIN A FEW DEGREES OF
SEASONAL NORMALS...RANGING FROM THE UPPER 50S FAR INLAND TO THE LOW
60S EAST. IT SHOULD BE NOTED THAT BREEZY TO GUSTY WINDS WILL DEVELOP
SUNDAY NIGHT THROUGH MONDAY AFTERNOON...AS AN IMPRESSIVE 50 KT LOW
LEVEL JET MOVES ACROSS THE AREA OVERNIGHT...AND A LARGE PRESSURE
GRADIENT DEVELOPS IN THE WAKE OF THE FRONT DURING THE DAYTIME HOURS.
WEST/NORTHWEST WINDS COULD PEAK AT 20 TO 30 MPH.

MONDAY NIGHT AND TUESDAY...THE PRESSURE GRADIENT WILL BEGIN TO
WEAKEN AS SURFACE HIGH PRESSURE MOVES INTO THE MID ATLANTIC AND
SOUTHEAST STATES...EVENTUALLY BECOMING LOCATED ALONG THE COASTLINE
BY TUESDAY AFTERNOON. A MUCH COOLER AIR MASS WILL HAVE MOVED INTO
THE REGION...AND EXPECT NOTABLY COLDER LOW TEMPERATURES MONDAY NIGHT
IN THE UPPER 20S INLAND TO THE LOW 30S CLOSER TO THE COAST. HIGH
TEMPERATURES ON TUESDAY WILL BE NEARLY 10 DEGREES COOLER THAN THE
PREVIOUS DAY...SUPPRESSED IN THE LOW TO MID 50S WITHIN SOLID
NORTHEAST FLOW.

LAKE WINDS...GUSTY CONDITIONS ARE EXPECTED ALONG THE LAKE SHORE OF
LAKE MOULTRIE MONDAY...HOWEVER MIXING WILL BE RESTRICTED SOMEWHAT
OVER THE BULK OF THE LAKE WATERS. AS A RESULT...THERE REMAINS SOME
UNCERTAINTY AS TO WHETHER A LAKE WIND ADVISORY WILL BE REQUIRED.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
TRANSIENT SURFACE HIGH PRESSURE WILL MOVE INTO THE ATLANTIC TUESDAY
NIGHT. A COASTAL TROUGH WILL ONCE AGAIN DEVELOP ALONG THE PERIPHERY
OF THE ATLANTIC HIGH ON WEDNESDAY...WHILE A SOUTHERN STREAM
SHORTWAVE DEVELOPS FAR TO THE WEST ACROSS TEXAS AND SUPPORTS THE
DEVELOPMENT OF A SURFACE LOW IN THE GULF OF MEXICO. ALTHOUGH THE
INITIAL SHORTWAVE WILL DAMPEN LATE WEDNESDAY...THE SURFACE LOW WILL
CONTINUE TO TAKE SHAPE AND MOVE EAST ACROSS THE GULF. NUMERICAL
MODEL SOLUTIONS DIVERGE QUITE NOTABLY REGARDING THE STRENGTH OF THE
LOW PRESSURE WAVE AND THE PRESENCE OF ADDITIONAL SHORTWAVE ENERGY
DIVING INTO THE GULF COAST STATES OR SOUTHEAST LATE THURSDAY INTO
FRIDAY. AS A RESULT...CONFIDENCE IN FORECAST DETAILS BECOMES RATHER
LOW FOR THE LATE WEEK PERIOD.

AFTER A PERIOD OF DRY WEATHER EARLY IN THE WEEK...HAVE REINTRODUCED
RAIN CHANCES BY WEDNESDAY TO ACCOUNT FOR MARINE SHOWERS PROGRESSING
ONSHORE FROM THE COASTAL TROUGH. HAVE THEN INCREASED RAIN COVERAGE
WEDNESDAY NIGHT INTO THURSDAY...AS MEDIUM RANGE MODELS ARE IN
GENERAL AGREEMENT THAT SOME DEGREE OF RAIN WILL BE AFFECTING THE
FORECAST AREA DURING THIS TIME FRAME. MODEL SOLUTIONS THAT INDICATE
THE SECOND WAVE OF UPPER LEVEL ENERGY LATE THURSDAY INTO FRIDAY
MAINTAIN RAIN COVERAGE ACROSS THE REGION ACCORDINGLY...YET WILL CAP
RAIN POTENTIAL NO HIGHER THAN SLIGHT CHANCE THROUGH FRIDAY UNTIL
MODELS COME INTO BETTER AGREEMENT. HAVE INDICATED RAIN CHANCES
FALLING BELOW 10 PERCENT BY SATURDAY...WITH ANY COASTAL LOW SYSTEM
LIKELY LIFTING AWAY BY THE WEEKEND.

HIGH TEMPERATURES WILL BE IN THE UPPER 50S TO LOWER 60S WEDNESDAY
AND THURSDAY AFTERNOONS...BEFORE A NOTABLE COOLING TREND OCCURS ON
THE BACK SIDE OF THE LOW PRESSURE SYSTEM FRIDAY AND SATURDAY.

&&

.AVIATION /16Z SATURDAY THROUGH WEDNESDAY/...
VFR WITH LIGHT WINDS THROUGH THE PERIOD.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS WILL PREVAIL UNTIL SUNDAY
NIGHT INTO MONDAY MORNING...WHEN MVFR OR POSSIBLY LOWER CONDITIONS
ARE LIKELY DUE TO A PASSING COLD FRONT. BREEZY CONDITIONS AND/OR
WIND SHEAR IS ALSO LIKELY SUNDAY NIGHT/MONDAY.

&&

.MARINE...
TODAY...EXPECT BOTH WINDS AND SEAS TO DIMINISH TODAY AS HIGH
PRESSURE SHIFTS SOUTH. GUSTY NORTH WINDS AND ELEVATED SEAS THIS
MORNING WILL DIMINISH THROUGH THE DAY AS THE PRESSURE GRADIENT
SUBSIDES...WITH WINDS VEERING TO NORTHEAST/EAST.

TONIGHT...EAST WINDS WILL VEER SOUTHEAST OVERNIGHT WITH WINDS
GENERALLY REMAINING LESS THAN 10 KT. SEAS WILL AVERAGE 1-2 FT
NEARSHORE WATERS WITH 2-3 FT OFFSHORE WATERS.

SUNDAY AND MONDAY...SURFACE HIGH PRESSURE WILL CONTINUE
TO TRACK INTO THE ATLANTIC SUNDAY. THE PRESSURE GRADIENT WILL THEN
TIGHTEN BETWEEN THE ATLANTIC HIGH AND AN UPSTREAM LOW AND TRAILING
COLD FRONT SWEEPING THROUGH THE MARINE ZONES MONDAY. COLD ADVECTION
THAT SUPPORTS MIXING INTO A NOTABLE 40 TO 50 KT LOW LEVEL JET WILL
EASILY ALLOW CONDITIONS TO REACH SOLID SMALL CRAFT ADVISORY
THRESHOLDS...WITH A RISK FOR POSSIBLE GALES ACROSS THE CHARLESTON
COUNTY WATERS AND OFFSHORE GEORGIA ZONES.

ALTHOUGH CONFIDENCE IS NOT HIGH ENOUGH TO INCLUDE EXPLICITLY IN THE
FORECAST...WILL CONTINUE TO NOTE THE SMALL POTENTIAL FOR SEA FOG
SUNDAY EVENING IF THE INCREASE IN WINDS ARE DELAYED...AS WELL AS A
RISK FOR SOME STRONGER THUNDERSTORMS OUT NEAR THE GULF STREAM IN
ADVANCE OF THE COLD FRONT.

TUESDAY THROUGH WEDNESDAY...A TRANSIENT HIGH PRESSURE WEDGE WILL
PREVAIL AS LOW PRESSURE EVENTUALLY DEVELOPS IN THE WEST/NORTHWEST
GULF AND A COASTAL TROUGH ATTEMPTS TO FORM NEARBY. LATEST PROGNOSIS
IS THAT CONDITIONS REMAIN BELOW THE ADVISORY CRITERIA DURING THIS
TIME.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...



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